Research On Key Control Technology Of Sensorless Sensor For Brushless DC Motor

Due to the advantages of long life,stable work,convenient maintenance,Brushless DC Motor(BLDCM)has a wide range of requirements in electrical equipment,transportation,aerospace and industrial automation.As the position sensor cannot be used in some harsh working environments,and sensorless can reduce the volume of the motor and decrease the difficulty and cost of machining,BLDCM mainly focuses on the research on the control strategy of rotor sensorless.In this paper,the rotor initial position identification and starting strategy,Back Electromotive Force(back-EMF)zero-crossing detection method,rotor position error and compensation analysis,system software and hardware design and other related problems were studied in depth.The main topics of this paper include the following directions:1.Sensorless starting strategy.The voltage pulse vector in different directions was injected according to the stator core saturation method,and the initial interval of the 30° electrical angle range of the rotor was determined according to the magnitude of the response current value.After accurately locating the rotor position,the BLDCM can be successfully started by a software using boost voltage and frequency method.2.Back EMF detection based on terminal voltage method.By detecting the voltage of the winding phase of the disconnected phase,the software calculation method and the hardware circuit extraction method are used to determine the zero-crossing point of the back electromotive force,and then delay the 30° electrical angle to obtain the position signal of the rotor.Correlation compensation correction was performed for the phase delay brought by the experiment.3.Back EMF detection based on disturbance observer.The back EMF of the nonlinear term in the BLDCM equation was regarded as the disturbance variable,and the disturbance observer structure was constructed based on the linear theory method.The principle and method of eliminating the observer output interference pulse by software were designed.The final experimental results show that the observer can obtain better position estimation accuracy.At last,the feasibility of the method was verified.4.System software and hardware design.The hardware part includes the control system based on TMS320F28335 and its peripheral circuits,and the drive system based on PS21865 and its protection circuit.The software part contains the program flow chart of the program main frame.The related control algorithm in this paper was verified on the designed experimental platform.